WPF CheckBox checked event on scrolling thought datagrid

I have a datagrid with a DataGridTemplateColumn containing a CheckBox. I create the column like this:

DataGridTemplateColumn cTemplateColumn = new DataGridTemplateColumn();
            cTemplateColumn.Header = "Auswahl";
            FrameworkElementFactory cFactory = new FrameworkElementFactory(typeof(CheckBox));
            Binding b1 = new Binding("[__intern_cv__]");
            //b1.IsAsync = true;
            b1.Converter = new StringToBoolConverter(this);
            b1.Mode = BindingMode.TwoWay;
            b1.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
            cFactory.SetValue(CheckBox.IsCheckedProperty, b1);
            cFactory.SetValue(CheckBox.HorizontalAlignmentProperty, HorizontalAlignment.Center);
            cFactory.AddHandler(CheckBox.CheckedEvent, new RoutedEventHandler(CheckedEvent));
            cFactory.AddHandler(CheckBox.UncheckedEvent, new RoutedEventHandler(CheckedEvent));
            cFactory.AddHandler(CheckBox.PreviewMouseDownEvent, new MouseButtonEventHandler(checkBoxMouseDown));
            DataTemplate cCellTemplate = new DataTemplate();
            cCellTemplate.VisualTree = cFactory;
            cTemplateColumn.CellTemplate = cCellTemplate;    
            Columns.Add(cTemplateColumn);

Now i have the problem, that during scrolling throught the DataGrid, the CheckedEvent is called, with Checked == False.

The vents a subscripted here:

cFactory.AddHandler(CheckBox.CheckedEvent, new RoutedEventHandler(CheckedEvent));
cFactory.AddHandler(CheckBox.UncheckedEvent, new RoutedEventHandler(CheckedEvent));

How can scrolling call the event?

maybe someone has an idea, thank you!